Process of roasting



. 1,644,692 Oct. 11, 1927- READ ET AL PROCESS OF ROASTING Filed July 29. 1925 A TTORNE Y Patented Oct. 11, 1927.

UN lT-ED STATES- 1,644,692 PATENT OFFICE.

JOHN BURlN'S READ, OF GOLDEN, AND MELVILLE F. COOLBAUGH, OF DENVER, COLO- RADO, ASSIGNORS TO THE COMPLEX ORES RECOVERIES COMPANY, 01 DENVER, COLORADO, A. CORPORATION OF COLORADO.

PROCESS OF ROASTING.

Our invention relates to the roasting of mineral sulfides and has particularly in view a means for balancing the temperatures during the roasting operation. The invention is practised articularly in connection with a process of roasting sulfides, wherein the air, oreand sulfur-containing gases travel concurrently or in the same direction through the furnace as disclosed in our Patent No. 1,582,347, dated April 27, 1926.

In'the concurrent roasting of sulfide ores, it has been observed that it is diflicult to maintain ignition in the top of the furnace, when'the fuel value ofthe ore is low, when feeding a large tonnage, or wet, or coarse material. To maintain the ignition, it is customary to use the hot air produced by cooling the central column and rabble arms of the furnace, but in certain instances this may not be sufficient.

The object of the present invention is to take heat, in the form of gas, away from the hottest zone of the furnace and transfer such heat to the incoming charge to evaporate moisture and ignite the ore.

The difficulty of maintaining ignition is overcome in this invention by introducing the air for oxidation ata point that is lower in the furnace than that at which the ore is introduced, preferably the second or third hearth, and allowing a portion of the air, and of the gases produced, to travel upward, and the rest to travel downward. That portion which travels upward is conducted by a series of'flues, either in the walls of the furnace or externally to the furnace, as shown in the drawings, and is r'e-admitted to the furnace, at or below the point at which the air is admitted, or it may even be turned directly into the flues. A series of dampers in conjunction with a fan, or Without a fan, where flue draft is sufficient, are employed to regulate the relative proportions of air and gases which travel upwardand downward.

In that section of the furnace where the gases are travelling upward, only that portion of the sulfide sulfur will be eliminated which will be necessary to keep the charge ignited; the main desulfidizing reaction will take place in that section of the furnace where the gases and solids are traveling concurrently.

By this process heat is taken from that section of the furnace which tends to become too hot, and is distributed to that section which it not hot enough. The heat roasted efficiently without the use of ex traneous fuel.

In the drawing, the process is disclosed as being carried out in a superposed hearth furnace, although other conventional types of furnace can, with suitable modifications, be used. 7

Referring to the drawing for a more complete disclosure of the invention Y The figure is a vertical section of one type of furnace suitably modified to carry out the process.

The furnace is-provided with a pluralit of superposed hearths 2 and a hollow vertical rotary shaft 3, having secured thereto rabble arms 4. Alternate hearths are provlded respectively with central openings 5 and peripheral openings 6,.throu h which the ore drops as it travels from earth to hearth.

The upperend of the hollow vertical shaft 3 is connected to a flue 7, which is provided with branches 8, 9, and 10 leadin into the space above the second, third, an fourth hearths and below the top hearth. The space above the top hearth is connected to a flue 11, which may be connected to a suction fan 12, the said flue 11 being provided with branch flues 13, 14,15 and 16, leading into the spaces above the hearths which are below the first hearth.

Ore is fed in through a hopper 17 at the top of the furnace, the calcined ore being discharged through an opening 18 in the bottom of the furnace. Cold air may be admitted through the branch flue 19 and the products of combustion may be in part, or completely, led off to a stack through the branch flue 20.

Valves 21 are suitablydisposed throughout the various flues for controlling the direction and amount of flow of the various gases.

Operation.

Ore is fed into the up er part of the furnace through the feed opper 17 onto the upper hearth. The roasting process will start by drying and igniting the sulfide ore on the first hearth. The ore will continue to roast on the hearths below the first hearth, and will be dischar ed, usually at a high temperature, throng the calcine discharg 18. Cold air fed into the bottom of the ho low column 3. will be substantially raised in tem rat'ure as it enters the flue 7 on its way I to t e branch flues 8, 9 and 10. The-air enterin through the flue 8 below the top heart will in a large art pass upward together with hot gases-into contact With the ore on the top hearth, providing thereby the necessary heat for drying the ore and effecting ignition. The heated air passing throu h the branch flues 9 and 10 will furnish t e necessary oxygen for combustion on the third and fourth hearths and lower hearths, the gases over these hearths traveling concurrently with the ore. It maybe advisable to use one, two, or three flues for the introduction of air to the furnace or any combination of flues 8, 9 and 10. In any combination for introducing air a portion of it will travel upward and the remainder downward.

The direction of flow of gases on the hearths will be controlledin part by the fan 12. The fan is rotated so that the gases above the top hearth will be drawn into the flue, 11, thus producing an upward current above the top hearths, whereas the fan will force the gases through the branch flues 13, 14, 15 and 16, or any of these, thus causing a downward movement of gases over the ore on these hearths. The ore is stirred and moved from hearth to hearth in the customa manner by the rotating rabble arms 4.

e claim 1. A method of roasting sulfides, which comprises feeding the sulfides into and throu h a furnace, feeding air for oxidation into t e furnace in advance of the point at which the sulfides are introduced and causing a portion of the hot gases to travel counter currently to carry heat to the introduced sulfids and causing-the remainder of the gases to travel concurrently with the ore.

2. A method for the concurrent roasting of sulfide ores which comprises moving the ore, air for oxidation, and sulfur-containing gases in the same direction through a furnace and feeding hot gases in rear of the oint at which the air for oxidation is intro uced to ignite the said sulfides.

3. A method for the concurrent roasting of sulfide ores, ore, air for oxidation and the sulphur-containing gases in the same direction through a furnace, and transferring gases from the hot zone of the furnace to the incoming charge to ignite the said ore.

4. A method for the concurrent roasting of sulfide ore, which com rises moving the ore, air for oxidation and t e sulfur-containing gases in the same direction through a furnace and transferring gases from the hot zone of the furnace in advance of the point of entry of the incoming ore, and to. the rear 2f the point of entry of the air for oxida- 5. A method of roasting sulfide ores, which comprises feeding the said sulfide mineral into and through a furnace, feeding hot gases countercurrently to the direction of the said ore, to ignite the said ore and eliminate such sulfide sulfur as will be necessary to keep the charge ignited and thereafter feeding air for oxidation to the said charge, and moving the said air, the sulfur containing gases and the ore in the same direction through the furnace, the main desulfidizing reaction taking place in that section of the furnace, when the gases and solids are travelling concurrently.

In testimony whereof, we aflix our signatures.

JOHN BURNS READ. MELVILLE F. GOOLBAUGH.

which comprises moving the 

